Does the coolant overflow need to be a closed system

[Classics Fan]

Originally Posted by Rust_never_sleeps

I was fixated on a smallish one for the front of the rad support, but it's 600ml, so probably a bit small. Most tanks aren't spec'd with volume, so trying for a similar shape with more capacity.
The two fender-curved options look good too:
OER 551448
OER 493072

Here’s how I have the Dorman 54002 mounted in my 71 Jimmy. The hose runs from the radiator overflow, under the fan shroud and up to the coolant reservoir. Don’t know why the pic is rotated 90*.